This application is a continuation-in-part of PCT Appln. No. PCT/EP94/00755 filed Mar. 10, 1994 and designating the United States.
1. Field of the Invention
The invention relates to a heating cycle system for a motor vehicle having an interior heat exchanger to receive heated coolant from an internal combustion engine and a circulating pump to deliver coolant as a liquid heat transfer medium. The system includes an independent heating unit to heat the coolant when it is not sufficiently heated by the engine.
2. Description of Related Art
Vehicle heating cycle systems in which a heat transfer medium can be heated by a heating device independent of the engine and circulated selectively either with the inclusion of an internal combustion engine in a large cycle (inline cycle) or by bypassing the latter via a bypass line in a small cycle which comprises only the motor vehicle heat exchanger and the heating device are known, as illustrated by German application DE-A1 40 22 731. In this system, the aforementioned operating modes are controlled by means of a valve which requires an additional electrical drive. This increases the installation cost and also, die to the additional parts, the failure probability of the system.